Tag: vfd

A device that converts alternating current with constant voltage and frequency into alternating current with variable voltage or frequency is called "variable frequency drive". VFD has the functions of voltage regulation, frequency modulation, voltage stabilization, speed regulation etc. VFD is generally used to control 3 phase AC motor in variable speeds. Now the three phase 220v-240v motor can run on single phase 120v power supply. ATO offers you 110v/120v input, 220v/230v/240v output VFDs. It can not only realize single phase input & output, but also convert single phase to three phase.

1 Electromagnetic Design

For a common asynchronous motor, major performance parameters considered in design include the overload capacity, start performance ,efficiency and power. As for a VFD, its breakdown slip is inversely proportional to the power frequency, and it can start directly when the breakdown slip is near 1, therefore, the overload capacity and start performance doesn’t need to consider, the key problem to be solved is how to improve the adaptability of the motor to non sinusoidal power supplies. Methods are as follows:

The functions of input line reactor
It can restrain harmonic current, improve power coefficient, weaken surge voltage in input circuit, the impact of current on VFD, the influences of power voltage, limit current surge caused by grid voltage change and switching surge, spike pulse or voltage defects in phase change of rectifying circuit, effectively protect VFD and improve power coefficient. Input line reactor not only can stop the disturbance from power grid but reduce the pollution of power grid by harmonic current produced by rectifying unit.

Variable Frequency Drive (VFD), aka variable speed drive (VSD), generally it's using for controlling 3-phase AC motor in variable speeds. It's important to know, control 1-phase motor speed by a VFD may cause overheat of the motor, as well as the service life. It's recommended to upgrade the motor to three phase AC motor, which you can also connect the 3-phase motor to single phase power supply by using a single phase to three phase VFD, then control the speeds. Anyway, in technical it's possible to use a VFD for single phase motor speed controls, here ATO will show you details about running a single phase motor on a VFD.

It is found that the speed of air compressor motor is proportional to the actual consumed power of the air compressor. Therefore, it is necessary to reduce the motor speed in order to reduce the actual consumption of the air compressor. The use of VFD in air compressor system can realize the real time control of motor speed (output power) without changing the air compressor motor torque through the accurate coordination of electrical control and frequency control in the air compressor system. To change the compressor speed to respond to the system pressure changes and to maintain stable system pressure can realize the output of high quality air pressure according to demand.

How to control the speed of three phase induction motor? The speed control method includes: changing the number of poles, stator voltage control, stator frequency conversion, cascade speed control, double-feed speed regulation, hydraulic coupler, electromagnetic slip clutch, etc.
The actual speed of three phase asynchronous motor is given by n=n_s (1 - s) =120f /p (1-s). It can be seen from the formula that the speed of 3 phase induction motor can be changed by the means of changing the number of induction motor’s poles "p", the slip "s" and the frequency of power supply"f".

The traditional industrial agitator usually conducts no regulation or regulates the speed in mechanical method. The speed regulation in mechanical method will increase the loss of the industrial agitator. Meanwhile, the industrial agitator will work in fluctuating status. Furthermore, it will also work in the status of "big rated power with small load power", which is quite not economic. The motor power of the industrial agitator in operating under the frequency conversion speed control is similar to its characteristics of the revolving speed and pump load. Using VFD for speed regulation will obtain a substantial power saving rate.

Computerized embroidering machine can realize traditional manual embroidery with high speed and high efficiency, and meet the requirement of multi-level, multi-function, unity and perfection which is out of reach of manual embroidery. Servo motor via its advantages plays an important role in various embroidery machines, to make sure the high quality in products.

Frequency conversion technology is utilized to realize soft start and soft stop. The characteristics of speed up and speed down are utilized to increase the start and stop time of the motor. Take the motor of 1.5KW as an example, the motor employs the slowdown motor with a reduction ratio of 1:10. Through the reversing gear, the motor will change from the revolving movement into the straight line movement. Each revolving will realize one pushing action. When the incense stick goes through the discharging bucket, the stirring device for discharging will be driven with the chain drive organization while the motor is revolving. The material pushing jacket will be filled with incenses and then be extruded outside through pushing. In addition, As to the pressure(discharging quantity), the operator can adjust the revolving eccentric wheel to change the journey of the material pushing jacket and increase its discharging space, thus achieving the pressure change. Completing the whole process only needs about 0.4s, then one incense stick is finished. The VFD has been debugged for incense stick manufacturing, so as to reach the manufacturing requirements thoroughly.

Loading trolley, uncoiling machine, board swaging device, six-layer straightening machine, tracking shearing system, conveying and lifting work platform, double-layer pneumatic layout shelf, hydraulic system, electrical control system. The overall system adopts the VFD, PLC, touch screen, rotary encoder and other components to constitute the automatic control system of the production line. Under the premise of giving consideration to both horizontal shearing precision and manufacturing efficiency, through utilizing the high-speed counting function of the PLC and the speed regulating and controlling function of the VFD, so as to control the starting, operating, speed reducing, crawling and accurate stopping of the straightening roll and pressing roll effectively, thus realizing the high-efficient and automatic cutting to length of the metal plate.

In the entire manufacturing process of the concrete pile, molding on the centrifuge is the most vital step. This process includes: Cloth distribution, second level transition, compacting three stages. Different stages have different requirements to the revolving speed and time of the tubular pipe. In addition, the tubular pipes of different wall thickness and length will have different requirements to the revolving speed and time of the three stages. This requires the VFD to be able to regulate the working stage of the motor according to the different types of concrete piles. It will operate different speed and time at different stages to ensure the product quality of the concrete pile.

VFD and the display control HMI touchscreen is communicating through MODBUS, so as to realize the stopping, frequency setting and status monitoring and other functions of the VFD through the HMI touchscreen.

The wire-cut EDM is to utilize the metal linear tool electrode (or named as wire electrode) to process workpieces with the principle of impulsive discharge to erode the metals. High speed wire-cut EDM is applied in the processing of the metal pieces with high precision, complicated shape, especially the mould and so on.

Because the induction motor has incomparable advantages: Simple and solid structure, cheap price, and easy maintenance. So using the means of VFD dragging three-phase induction motor replaces the means of traditional speed regulating, can solve the problem of high failure rate of the tower crane fundamentally. Moreover, it has advanced technology and significant energy saving effect. It is the ideal transmission controlling device of the tower crane.

The overhead crane is a kind of hoisting machinery with quite extensive application in the industrial and mining enterprise. Its operating organism is constituted by three basically independent dragging systems, which are respectively the cart dragging system, dolly dragging system and hook dragging system. This article ATO will take the practical application of VFD for overhead crane improvement in thermal power plant as the example, illustrating the application and improvement scheme of VFD for the overhead crane comprehensively.

The VFD speed control system regards the network pressure as the control object. The pressure transmitter changes the pressure in the air storage tank into the electrical signal to send into the PID regulator inside the VFD, so as to compare with the pressure setting value. Then calculation will be made according to the set PID control mode based on the difference value. The control signal will be generated to control the output signal and inverter frequency of the VFD, thus adjusting the revolving speed of the induction motor, so as to maintain the practical pressure to be always as the setting pressure.

According to the manufacturing technology of the hydroextractor, the multi-speed functional control of the VFD can be used. The hydroextractor with VFD control system belongs to the approximate constant torque load with big inertia. Therefore, the system requirements can be reached by configuring braking unit and braking resistor on the basis of selecting the AC converter. The built-in braking unit of the30hp VFD and below can not only save space, but also save the cost.

This article ATO summarizes how to apply and debug the VFD for the circular knitting machine in one textile mill. ATO chooses the non-inductive vector VFD. It adopts current vector control, its precise control as well as the characteristics of low-frequency stability and large torque, realizing the functions of big starting torque, stable operation, quick stop and so on of the circular knitting machine.

The working principle of the automatic industrial washing machine is: under the unified deployment and management of the time schedule controller. The VFD controls the induction motor to carry out positive and negative revolving uninterruptedly, thus achieving the non-synchronous movement of the water and the clothes, so as to enable the water and the clothes to rub and knead, thus being cleaned.

For a long period, the chemical, cement, ceramic industries and so on normally adopt the ball mill to grind the raw materials. Usually, the decompression start-up mode is employed. The high starting current has great shocks to the equipment and power grid. Meanwhile, in working frequency, it is easily to over grid the materials. The required grinding circle is long, with low grinding efficiency and high unit product consumption. This promotes people to study and develop the ball mill system with smooth start, high grinding efficiency, high output and low consumption. This is exactly the VFD control system.